Minimally invasive instruments and methods for accessing the spinal column minimize tissue retraction and dissection in order to promote healing and faster recovery times. One or more retractors can be positioned in an access portal to facilitate access to locations deep within the body while maintaining the minimally invasive character of the procedure. The smaller access portals can increase the difficulty in determining the optimal length for the retractor since measurement devices placed in or through the portal include indicia or markings obscured by the skin or tissue below the incision or by other instruments positioned in the access portal. Systems and methods which improve the ability to measure and determine optimal retractor length for positioning in minimally invasive access portals are desirable.